[windows] imgpkg does not have a deterministic push across OS

**What steps did you take:**

On Windows
```
> git clone https://github.com/vmware-tanzu/carvel-imgpkg
> cd carvel-imgpkg
> imgpkg push -i image-windows -f test/e2e/assets/simple-app --yes
Succeded pushing sha sha256:73e65af5e889da98ece0bd471b2cd83baac574e19943108212ba0417ff8f03c2
```

On Linux
```
> git clone https://github.com/vmware-tanzu/carvel-imgpkg
> cd carvel-imgpkg
> imgpkg push -i image-linux -f test/e2e/assets/simple-app --yes
Succeded pushing sha sha256:ceef30cbdce418efde0284f446df9cec9e535adcd6e1010dad30ddae1dc9367b

> imgpkg pull -i image-linux -o /tmp/linux
> imgpkg pull -i image-windows -o /tmp/windows
```

```
ls -l /tmp/windows
total 48
-rw------- 1 dennisleon wheel 11558 Dec 31 1969 LICENSE
-rw------- 1 dennisleon wheel 98 Dec 31 1969 README.md
drwx------ 2 dennisleon wheel 64 Dec 31 1969 config
-rw------- 1 dennisleon wheel 25 Dec 31 1969 config\config.yml
drwx------ 2 dennisleon wheel 64 Dec 31 1969 config\inner-dir
-rw------- 1 dennisleon wheel 6 Dec 31 1969 config\inner-dir\README.txt

ls -l /tmp/linux
total 32
-rw------- 1 dennisleon wheel 11357 Dec 31 1969 LICENSE
-rw------- 1 dennisleon wheel 95 Dec 31 1969 README.md
drwx------ 4 dennisleon wheel 128 Oct 6 11:25 config
```

**What happened:**
Image pushed resulted in a different sha (and different contents) across windows and linux

**What did you expect:**
The same image pushed. Or a way to differentiate between an image built for windows vs linux. Using an Image Index perhaps?

**Environment:**

- imgpkg version (use `imgpkg --version`): 0.19.0
- Docker registry used (e.g. `Docker HUB`):
- OS (e.g. from `/etc/os-release`): Windows 10

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Reproduce the Windows and Linux commands using test/e2e/assets/simple-app, then trace the imgpkg push and pull entry points that handle archive paths and image metadata. Done means the same content produces the same digest across both operating systems, or the supported platform-specific image/index behavior is clearly established and tested.

Written by the indexing model from the issue text.